The Eisenhower and Johnson memorial tunnels feature 28, 10.5-foot diameter fans that pull clean air into the tunnel from outside and pump bad air out. The ventilation system is touted by tunnel employees as the most important safety system.

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This is the second in a series on the Eisenhower/Johnson Memorial Tunnel, which turned 40 this year.

When workers finally detonated the first sticks of dynamite on March 15, 1968, the Eisenhower Tunnel project was slated for completion in three years at an estimated cost of a little more than $50 million. When it opened on March 8, 1973, it was two years behind schedule and more than 100 percent over budget.

Despite the rocky start, the Eisenhower/Johnson Memorial Tunnel may have inadvertently benefited from innovative practices and technology as a result of the delay. Today the tunnels have a reputation for safety and to date more than 350 million cars, trucks and buses have traveled through close to 9,000 feet of highway under the Continental Divide. There has never been a fatality.

“That’s not luck and it hinges a lot on our surveillance system,” said tunnel maintenance superintendent Michael Salamon. “In my opinion, I think it is the safest 2 miles of highway in the state system.”

More than 50 multi-skilled workers, including electronics specialists, mechanical engineers and electricians, not only perform their duties, but also plow roads, man the control room and respond to fires.

Those workers also have ensured that much of the technology protecting motorists and employees has survived the more than 40 years since it was installed. Almost everything in the tunnel is original, Salamon said, from its 72,000-gallon-per-day water-treatment plant to its highly touted ventilation system, which boasts 28 fans, each of them 10½ feet in diameter.

The fans are located in ventilation houses at each end of the tunnels, with 14 serving as exhaust fans to pump bad air out of the tunnels and 14 serving as supply fans to bring clean air in.

Powered by electricity and boasting up to 600 horsepower, each fan is capable of moving 543,000 cubic feet of air per minute.

“The ventilation system is our most essential system,” Salamon said. “We could operate without lighting and you could even deal with a dirt road if you had to, but you have to keep your air quality at safe levels. I’m proud we’re looking at 40-year-old motors that are still operational.”

The air quality is monitored 24 hours a day, seven days a week in a control room by two to three tunnel employees at all times, Salamon said. Carbon monoxide levels are monitored and transmitted to the control room by 14 detectors strategically positioned throughout the tunnels, seven in each portal.

According to the U.S. Department of Health and Human Services, carbon monoxide levels of 100 parts per million for a period of 15 minutes would be considered a violation. On Wednesday of last week, carbon monoxide levels were dancing between 10 and 20 parts per million, with only two fans running in each tunnel and at their lowest speeds.

“This is probably as clean as standing on Colfax and Colorado Boulevard (in Denver),” Salamon said.

In addition to air quality, control room operators monitor traffic and keep a close watch for potential safety threats using a system of more than 100 cameras that not only cover every inch of the tunnels, but also provide views down each side of the highway corridors, as well as to Loveland Pass. With so many cameras at their disposal, the operators have no blind spots, Salamon said.

On average, tunnel employees respond to about 400 motorist-assist situations each year.

Due to the steep grades on either side of the tunnel, coupled with automobile engines working less efficiently at elevation than at sea level, Salamon said a majority of the motorist-assist emergencies they respond to are stalled vehicles.

However, contrary to popular belief, tunnel employees respond to an average of three vehicle fires inside the tunnels every year. The surveillance system has played an instrumental role in ensuring that none of those fires was fatal.

On one occasion in the 1980s a truck with a bed-mounted camper was spotted by a down-corridor camera smoking as it neared the tunnel. Fearing the truck might burst into flames, control room operators stopped traffic in both directions as the camper entered the tunnel.

As feared, it ignited about 200 yards before it exited the Summit County side of the tunnel. What made that fire particularly memorable, Salamon said, was that the bed-mounted camper was equipped with a propane stove. The propane bottles the driver used to fuel that stove exploded and the fire burned so hot it melted concrete and some of the wall tiles.

Still, thanks to the surveillance system, no one was injured and one tunnel employee was able to respond to the fire and extinguished it himself using the tunnel’s largest pumper truck.

In the third part of this series we’ll take a deeper look at the future of fire safety in the tunnels and how the coming fire suppression system may ignite a debate to have the Colorado Department of Transportation’s policy prohibiting HAZMAT transports through the tunnels changed.